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Building Codes & Design Standard

Building Codes & Design Standard

Building codes influence many aspects of energy consumption and greenhouse gas emissions. ...


Building Codes and Design Standards

Codes that play a role (good or bad) in decarbonization of healthcare facilities

Title 24 (California)

      1. Part 4: California Mechanical Code
      2. Part 6: California Energy Code
      3. Part 11: California Green Building Standards Code


      1. Standard 170: Ventilation of Health Care Facilities
      2. Standard 90.1: Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings
      3. Standard 228: Standard Method of Evaluating Zero Energy and Zero Net Carbon Building Performance
      4. Standard 100: Energy Efficiency in Existing Buildings

Existing codes that impact decarbonization

The ASHRAE Task Force for Building Decarbonization put an interim document together summarizing all of ASHRAE's current Standards and Codes that impact decarbonization.


Table 1: ASHRAE Task Force for Building Decarbonization Interim Product: Standards and Codes Table

Discussions around current codes that impact decarbonization

We are getting closer to improving building codes but hospitals are still bound by older codes. The CMS codes need to be changed first. The federal government and CMS need to help improve healthcare energy codes. Some issues are around emergency generators. Diesel generators are still required for backup power but newer technology like battery storage and fuel cells could replace diesel generators and provide the facility with ways to obtain cleaner energy and use storage for cost and carbon advantages, such as using stored power at peak demand hours and carbon-intensive production hours, and storing it during non-peak demand hours and low-carbon production hours. See duck curve.

Healthcare specific codes need to be more open to new innovations and research into emerging technologies.

It also takes a long time to move anything through a code cycle process and for changes to take effect. The process is usually 3-4 years long.

Most codes have a bigger impact on new construction than they do on existing buildings but existing buildings are a large source of carbon emissions. States need to develop codes to address existing buildings and how they can improve. For example, the state of WA recently passed a law to regulate commercial building energy usage and WA also has state codes that regulate HVAC system efficiency. They build in the demand of the market.

Prescriptive options and outcome-based paths are the best way to ensure the codes are meaningful and they leave the design teams with flexibility on how they can address the measures.

Architecture has a lot to do with sustainable design as well. See ASHRAE 189.3 Design, Construction, and Operation of Sustainable High-Performance Health Care Facilities (ANSI Approved; ASHE Co-sponsored) for sustainable design guidance. ASHRAE is working on a new standard, 227P, for passive building design.

California Codes

Title 24, Part 4: California Mechanical Code

Encourage Variable Air Volume (VAV)

Many of California’s 340 hospitals are still operating as constant volume because the current California Mechanical Code does not require VAV, and actually discourages the implementation of VAV by requiring automatic modulating dampers for every space. These return air devices add significant cost to the project and are often value engineered out of the final design. The result is a hospital that ventiates at the maximum demand ventilation setting 8,760 hours a year. Supplying this much conditioned air results in extremely high consumption of natural gas heating energy, cooling energy, and fan energy.

A code change that was approved for the 2022 California Mechanical Code effective Jan 1, 2023, will remove the requirement for automatic modulating dampers in the return or exhaust for all zones. With this new code change, the barrier of added construction cost is removed and a retrofit of all existing buildings’ ventilation systems should be completed as soon as possible to reduce natural gas consumption across the state.

Section 407.5 Variable Air Volume.

407.5.1.3 Variable air volume for return or exhaust air shall be accomplished by utilizing Spaces with pressure requirements per Table 4-A shall utilize an automatic modulating damper in the return or exhaust air for each zone space. The damper will modulate from full open to minimum position in conjunction with the supply air VAV terminal boxes equipment.

Reduce patient room minimum ventilation requirements

Section 4 describes the requirements for ventilation in California hospitals. Minimum ventilation rates are identified in Table 4-A, which is derived from ASHRAE Standard 170. These minimum ventilation rates are defined in air changes per hour (ACH). However, these codes are not evidence-based. A research project was conducted in a CA hospital to prove the hypothesis that these ACH rates are resulting in overventilation of hospital facilities and as a result, an excess use of natural gas for the purpose of reheating supply air. In a VAV system, a potential code change that would have a big impact on the natural gas consumption of a hospital, is reducing patient room minimum ventilation rates from 4 ACH to 1 or 2 ACH. By reducing the minimum ventilation rate by half or three-quarters, it will result in less natural gas use, less cooling energy, and less HVAC fan energy.

Title 24, Part 6: California Energy Code and Part 11: California Green Building Standards Code

Require VAV

The California Mechanical Code still allows constant volume re-heating zones in hospitals. All spaces, including administrative areas, are permitted to ventilate at full volume with cool air, and reheat. A hospital with constant volume zones could conserve energy with variable volume systems. California Building Energy Efficiency Standards (Title 24, Part 6) require variable air volume in most other commercial spaces; the project team recommends this requirement be extended to hospitals.

Remove hospital exemption to Energy Code

Hospitals were fully exempt from the California Energy Code until 2019. After that date, hospitals were required to meet part of the Energy Code, including requirements for lighting, building envelope, and minimum efficiency for chillers. However, removing further exemptions of the energy code for hospitals would require facilities to meet stricter energy consumption guidelines and result in reduced energy use. See State of WA Department of Commerce Clean Buildings Bill.


ASHRAE Standard 170, Ventilation of Health Care Facilities


Reheat in hospitals is a big portion of the energy usage and emissions from hospitals. The reason for the reheat is primarily because the hospitals have to meet the air change requirements in ASHRAE 170, which causes excess use of fan, heating and cooling energy. Many of the air change requirements in ASHRAE 170 have been around for decades. As such, there is little evidence as to how they were established, but they have been proven to not put the patient and staff at risk. The challenge in getting the requirements reduced is there needs to be evidence that it will not put patients, staff and visitors at risk and that takes time and money to fund but can be done. In addition, when evaluating potential changes, the committee has to consider that the Standard is used throughout the country (and in others) and in all climates from hot and humid to cold and dry.


The process for changing the code can be time consuming. Because it is an ANSI document, each proposed change has to go through one and sometimes multiple public reviews. And this is after the committee vets it. This means that while ASHRAE 170 is a continuous maintenance document (changes can be published in between full document publication cycles), it can still take 6 months to two years to get a change made, Complicating matters further, even though 170 may adopt a change, depending on what State you are in and whether they allow addenda to be enforced once they are approved, it may not be in effect until the State adopts it and/or CMS (Centers for MediCare and Medicaid) and adopts it.

Recent changes

There have been some changes to 170 in the last 10 years which allow healthcare facilities to reduce their energy consumption. These include:

  1. Patient room minimum total air changes per hour was dropped from 6 to 4. (2013)
  2. Laboratories can utilize a risk assessment of active sensing of contaminants to reduce laboratory air changes. (2015)
  3. General Exam room minimum total air changes per hour was dropped from 6 to 4. (2016)
  4. The code was changed in 2013 to allow displacement ventilation in patient rooms. Studies have demonstrated that displacement ventilation may improve indoor air quality and can be more energy efficient by focusing ventilation on the breathing zone. The code was revised again in 2017 to reduce the energy benefit of displacement ventilation.
  5. Table 7.1, 8.1 and 9.1 have a new column added which makes it clear which spaces are permitted to reduce airflow when unoccupied. (2021)
  6. Addendum to allow Natural Ventilation in certain Healthcare spaces. (2022)

Other potential code changes being discussed:

  1. Lower Patient Room Air changes even further.

ASHRAE Standard 90.1, Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings

90.1 vs California

ASHRAE Standard 90.1 requires VAV in all facilities. For states that adopt 90.1, this includes controls in the zone to turn down to the minimum code-required ventilation rate, which in many spaces is 4 or 6 air changes per hour (ACH).

For facilities with operating suites, this also means there is a need to have controls capable of reducing ventilation down to 20 ACH.

However, California Title 24 does not require VAV in healthcare buildings, though it is now permitted by the California Mechanical Code.

ASHRAE Standard 228-2023, Standard Method of Evaluating Zero Net Energy and Zero Net Carbon Building Performance

ASHRAE has released a new standard to measure zero net carbon and energy goals in buildings.

ANSI/ASHRAE Standard 228-2023, Standard Method of Evaluating Zero Net Energy and Zero Net Carbon Building Performance, sets requirements for evaluating whether a building or group of buildings meets a definition of “zero net energy” or a definition of “zero net carbon” during building operation. The standard draws from ASHRAE Standard 105, among others, to address energy and carbon flows across a site boundary, their measurement, and their balance.

“Achieving a zero energy building has been viewed by many as a difficult goal to meet, with unforeseeable roadblocks and differing guidance,” said Keith Emerson, P.E., Life Member ASHRAE, chair of the Standards Project Committee 228. Standard 228 provides a consistent method for determining whether new and existing sites have reached zero energy. We hope this standard will become a helpful resource for building professionals in strategic decarbonization planning.”

Additional features of Standard 228 are as follows:

  • Allowances for sites that lack the opportunity to produce adequate renewable energy, while placing additional requirements on the use of external carbon and renewable energy in the calculation.
  • Defined calculation of energy in terms of source—a multiplier on the energy crossing the site boundary to include energy used or lost in extraction, generation and transit to the site.
  • The main energy calculation made in terms of annual average factors. Allowance is made for the calculation of individual hours where data is available.

Standard 228 does not apply to the establishment of building energy performance goals or limits; design guidance or design requirements; embodied energy of building materials and systems; and transportation to and from a building. The standard is also not intended to circumvent any safety, health, or environmental requirements.


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